Xamarin.Forms TabbedPage event when the current tab is used to refresh the page

Question

I use Xamarin.Forms to create an iOS / Android application and have TabbedPage.

If the user is already on tab 2 and clicks Tab2, and I want to either update tab2 or execute the function myself so that I can update it myself.

Is there a way to do this inside Xamarin.Forms, or is there a way to do this using custom renders?

Answer 1

. My TabbedPage NavigationPage , , , , . "" OnTabbarControllerItemSelected iOS OnTabbarControllerItemSelected Android. .

Android Renderer ( )

using Android.Support.Design.Widget;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using Xamarin.Forms.Platform.Android.AppCompat;
[assembly: ExportRenderer(typeof(MainTabbedPage), typeof(MainPageRenderer))]
namespace YourNameSpace
{
    public class MainPageRenderer : TabbedPageRenderer, TabLayout.IOnTabSelectedListener
    {
        private MainTabbedPage _page;
        protected override void OnElementChanged(ElementChangedEventArgs<TabbedPage> e)
        {
            base.OnElementChanged(e);
            if (e.NewElement != null)
            {
                _page = (MainTabbedPage)e.NewElement;
            }
            else
            {
                _page = (MainTabbedPage)e.OldElement;
            }

        }
        async void TabLayout.IOnTabSelectedListener.OnTabReselected(TabLayout.Tab tab)
        {
            await _page.CurrentPage.Navigation.PopToRootAsync();
        }
    }
}

iOs Renderer:

using UIKit;
using System;
using Xamarin.Forms;
using Xamarin.Forms.Platform.iOS;

[assembly: ExportRenderer(typeof(MainTabbedPage), typeof(MainPageRenderer))]
namespace YourNameSpace
{
    public class MainPageRenderer : TabbedRenderer
    {
        private MainTabbedPage _page;
        protected override void OnElementChanged(VisualElementChangedEventArgs e)
        {
            base.OnElementChanged(e);

            if (e.NewElement != null)
            {
                _page = (MainTabbedPage)e.NewElement;
            }
            else
            {
                _page = (MainTabbedPage)e.OldElement;
            }

            try
            {
                var tabbarController = (UITabBarController)this.ViewController;
                if (null != tabbarController)
                {
                    tabbarController.ViewControllerSelected += OnTabbarControllerItemSelected;
                }
            }
            catch (Exception exception)
            {
                Console.WriteLine(exception);
            }
        }

        private async void OnTabbarControllerItemSelected(object sender, UITabBarSelectionEventArgs eventArgs)
        {
            if (_page?.CurrentPage?.Navigation != null && _page.CurrentPage.Navigation.NavigationStack.Count > 0)
            {
                await _page.CurrentPage.Navigation.PopToRootAsync();
            }

        }
    }
}

Answer 2

Android Native TabLayout, OnTabReselected

TabbedPageRenderer . OnTabReselected .

, TabbedPage OnTabReselected, :

[assembly: ExportRenderer(typeof(Page1), typeof(MyTabPageRender))]
namespace XamarinTabbedPage_Demo.Droid
{
    public class MyTabPageRender : TabbedPageRenderer, TabLayout.IOnTabSelectedListener
    {
        protected override void OnElementChanged(ElementChangedEventArgs<TabbedPage> e)
        {
            base.OnElementChanged(e);
        }
        void TabLayout.IOnTabSelectedListener.OnTabReselected(TabLayout.Tab tab)
        {
            int selectedIndex = tab.Position;
            if (Element.Children.Count > selectedIndex && selectedIndex >= 0)
            {
                Element.CurrentPage = Element.Children[selectedIndex];

                if (selectedIndex == 0)
                {
                    Element.CurrentPage.BackgroundColor = Color.Black;
                }
            }
        }
    }
}

Answer 3

You can put each tab on a different page, and then when a page is entered into the table, the method is called Override on Appearing()and you can update the values.